Wire-cut electroerosion, also called traveling-wire electroerosion, is well known in which an electrode wire axially advancing from a wire dispensing site to a wire takeup site is supported by a pair of wire guide members disposed at opposite sides of a workpiece. These guide members are provided to establish a straight-line path which traverses the workpiece and along which the wire is desired to travel to provide a renewing elongate electrode surface for electroerosively cutting the workpiece along a programmed cutting path in a plane transverse to the renewing electrode surface. While the renewing electrode surface must be of high straightness to assure due electroerosive cutting accuracy, it has been found that the wire in the cutting zone tends to bend backwards and uncontrolledly fluctuate in position due to a machining pressure that develops in the erosion gap, thus limiting the cutting accuracy obtainable. Furthermore, the wire, as thin as 0.5 mm or less in all sectional directions, inherently breaks once some excessive thermal stress concentrates in the cutting zone.
Instead of a wire, a tape-form electrode may be employed to provide a breakage-free traveling-electrode cutting operation. Also, when oriented to make its width in alignment with a cutting direction, the electrode tape is highly resistant to deflection and mispositioning. When the cutting direction changes, however, the tape must be inclined and such positioning stability of the tape is no longer the case. Since the erosion gap then lies defining with one lateral surface of the tape, the tape tends to deflect backwards. Thus, while a tape-form electrode gives rise to substantially greater advantages than a wire-form electrode as used in traveling-wire electroerosive cutting operations, it has been found that there still remain severe limitations in improving the cutting accuracy and efficiency achievable in those operations.